linux-kernel - Re: [PATCH v5 00/13] KVM/X86: Introduce a new guest mapping interface

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Date:   Wed, 30 Jan 2019 18:14:03 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Raslan, KarimAllah" <karahmed@...zon.de>,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>
Subject: Re: [PATCH v5 00/13] KVM/X86: Introduce a new guest mapping interface

On 25/01/19 19:28, Raslan, KarimAllah wrote:
> So the simple way to do it is:
> 
> 1- Pass 'mem=' in the kernel command-line to limit the amount of memory managed 
>    by the kernel.
> 2- Map this physical memory you want to give to the guest with
>       mmap("/dev/mem", physical_address_offset, ..)
> 3- Use the user-space virtual address as the "userspace_addr" field 
>    in KVM_SET_USER_MEMORY_REGION ioctl.
> 
> You will also need this patch (hopefully I will repost next week as well):
> https://patchwork.kernel.org/patch/9191755/

I took a look again at that patch and I guess I've changed my mind now
that the kernel provides e820__mapped_any and e820__mapped_all.
However, please do use e820__mapped_any instead of adding a new function
e820_is_ram.

Thanks,

Paolo

> I will make sure to expand on this in the cover letter in v6.